Robot having obstacle avoidance mechanism

ABSTRACT

A system includes a driver robot having a body with a pair of spaced apart flux conductors, and a follower robot having an articulated body with a pair of spaced apart magnets. The magnets are coupled to the flux conductors when the articulated body is in an engaged position. One of the magnets is decoupled from one of the flux conductors when the articulated body is in a flipping or stepping position.

This is a divisional of U.S. Ser. No. 13/214,143 filed Aug. 19, 2011.U.S. Ser. No. 13/214,143 claims the benefit of priority of provisionalapplication 61/481,165 filed Apr. 30, 2011, which is incorporated hereinby reference.

BACKGROUND

During assembly of an aircraft, fastening operations are performedsynchronously on opposite sides of various structures. A fasteningoperation may include drilling, countersinking and fastener insertion onone side of a structure, and terminating the end of each insertedfastener on the opposite side of the structure.

Consider fastening operations on a wing box of an aircraft. Drilling,countersinking and fastener insertion are performed by a robotic systemoutside the wing box. Sleeve and nut placement are performed inside thewing box by manual labor. A person enters a wing box through a smallaccess port, and performs the sleeve and nut placement with hand toolswhile lying flat inside the wing box. On the order of several hundredthousand fasteners are installed and terminated on common aircraftwings.

It would be highly desirable to eliminate the manual labor and fullyautomate the fastening operations on both sides of the wing box.However, while placing a nut over the threads of a bolt might be asimple task for a human, it is not so simple for a robot. Precisepositioning and orientation of a nut over a bolt is a complex task.

This task becomes even more complex due to space constraints inside thewing box. The wing box forms a narrow space that, at the tip, is onlyseveral inches high (see FIG. 5 for an example of a wing box). Moreover,the narrow space is accessible only through an access port. The robothas to enter the narrow space via the access port, navigate paststringers inside the narrow space, locate ends of inserted fasteners,and position an end effector and place a sleeve and nut over eachfastener end.

The task becomes even more complex because aircraft tolerances areextremely tight. The task becomes even more complex because the endeffector typically weighs 40 to 50 pounds. The task becomes even morecomplex because the robot inside the narrow space has to synchronize itstasks with those of the robotic system outside the wing box.

SUMMARY

According to an embodiment herein, a system includes a driver robothaving a body with a pair of spaced apart flux conductors, and afollower robot having an articulated body with a pair of spaced apartmagnets. The magnets are coupled to the flux conductors when thearticulated body is in an engaged position. One of the magnets isdecoupled from one of the flux conductors when the articulated body isin a flipping or stepping position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is an illustration of system including a robot and a fluxconducting device.

FIG. 1 b is a photograph of a robot that was actually reduced topractice.

FIG. 2 is an illustration of a general method of moving the robot toavoid an obstacle on a surface of a panel.

FIGS. 3 a to 3 p are illustrations of a particular method of moving therobot to avoid an obstacle on a surface of a panel.

FIGS. 4 a to 4 h are illustrations of another particular method ofmoving the robot to avoid an obstacle on a on a surface of a panel.

FIG. 5 is an illustration of an aircraft wing box.

FIG. 6 is an illustration of a system including inner and outer robotsfor performing a manufacturing operation on the wing box.

FIG. 7 is an illustration of a method of manufacturing an aircraft wingbox.

FIGS. 8 a-8 d are illustrations of a method of loading an inner robotinto a wing box.

FIG. 9 is an illustration of an embodiment of the inner robot.

DETAILED DESCRIPTION

FIG. 1 a illustrates a system 110 including a robot 120 for moving alonga first surface (S) of a non-magnetic panel 100 (e.g., a panel 100 madeof aluminum or a composite). The robot 120 includes a body 130, andfirst and second feet 140 and 145 connected to the body 130 via revolutejoints 132 and 134. The feet 140 and 145 may be pivoted about therevolute joints 132 and 134. Actuators (not shown) may be used to movethe body 130, or the feet 140 and 145, or both. At very least, each foot140 and 145 may be individually lifted off and raised above the firstsurface (S).

A first magnet 150 is located at the base of the first foot 140, and asecond magnet 155 is located at the base of the second foot 145. Themagnets 150 and 155 may be permanent magnets or electromagnets.Permanent magnets are preferred because they provide sufficient force ina lightweight compact package, and they don't require power.

FIG. 1 b shows a robot 120 that was actually reduced to practice. Theactuators are referenced by numerals 142 and 147.

Returning to FIG. 1 a, the system 110 further includes a driver 160positioned along a second surface (E) of the panel 100, opposite therobot 120. The driver 160 includes a chassis 170 and first and secondflux conductors 180 and 185 mounted to the chassis 170. The fluxconductors 180 and 185 may be aligned with the first and second magnets150 and 155. To align the first flux conductor 180 with the first magnet150, projections on the flux conductor 180 are aligned with projectionson the first magnet 150. These aligned projections form an air gap(across the panel 100) and define a minimum reluctance position formagnetic flux (F1). Deviation from that aligned position (as illustratedin FIG. 1) will increase the reluctance. Thus, movement of the firstflux conductor 185 out of alignment will be resisted. Conversely, whenthe first flux conductor 180 is moved towards the first magnet 150, theywill be forced into alignment in order to reduce the reluctance. Thesecond flux conductor 185 and the second magnet 155 define a minimumreluctance position for magnetic flux (F2) and interact in the samemanner.

In this manner, the robot 120 and the driver 160 are magneticallyattracted through the panel 100. When the first flux conductor 180 orthe second flux conductor 185 or both flux conductors 180 and 185 arealigned with the magnets 150 or 155, the robot 120 is clamped againstthe first surface (S) of the panel 100 and the driver 160 is clampedagainst the second surface (E) of the panel 100.

The driver 160 further includes a system for moving the driver 160 alongthe exterior surface (E) of the panel 100. For example, the system maybe a traction system including a wheel 190 driven by an electric motor(not shown), and a passive wheel 195.

When the magnets 150 and 155 are aligned with their corresponding fluxconductors 180 and 185, the driver 160 is magnetically clamped to therobot 120. When the driver 160 moves along the second surface (E) of thepanel 100, the robot 120 is pulled along the first surface (S). Themagnets 150 and 155 have sufficient strength to pull the driver 160against the exterior surface (E) of the panel 100 to create tractionbetween the driven wheels 190 and the exterior surface (E).

The magnets 150 and 155 also have sufficient strength to hold the driver160 against second surface (E). Consequently, the driver 160 may besupported against gravity without any external scaffolding or othersupport.

In some embodiments, each foot 140 and 145 is raised with sufficientpower to overcome the magnetic coupling and pull its magnet 150 or 155away from its corresponding flux conductor 180 or 185. In otherembodiments, the two flux conductors 180 and 185 can slide on prismaticjoints on the base 170 to engage and disengage the magnets 150 and 155.

During operation, the robot 120 can avoid obstacles on the first surface(S). FIG. 2 illustrates a general method of moving the robot 120 toavoid an obstacle. The robot 120 avoids the obstacles while holding thedriver 160 against gravity.

Additional reference is made to FIG. 2. At block 210, the robot 120 isplaced on the first surface (S) of the panel 100. At block 220, thedriver 160 is positioned on the second surface (E) of the panel 100,opposite the robot 120, with each foot 140 and 145 magnetically coupledto its corresponding flux conductor 180 and 185. Thus, the driver 160 ismagnetically clamped to the robot 120.

At block 230, the driver 160 moves along the second surface (E) of thepanel 100. Since the robot 120 is magnetically coupled to the driver160, the robot 120 is pulled along the first surface (S) and staysaligned with the driver 160. The robot 120 is moved until an obstacle isencountered. The robot 120 may use sensors to detect obstacles, or itmay use preprogrammed data that identifies the locations of obstacles.

At block 240, the robot 120 steps over the obstacle. This steppingfunction may include decoupling one of the feet 140 or 145 from its fluxconductor 180 or 185 (block 242), lifting the decoupled foot 140 or 145above the obstacle (block 244), and moving the robot 120 so thedecoupled foot 140 or 145 moves past the obstacle (block 246). Thedecoupled foot 140 or 145 may then be lowered back onto the firstsurface (S) after the obstacle has been stepped over, and thenmagnetically re-coupled with a flux conductor 180 or 185 (block 248).

Reference is now made to FIG. 3 a-3 p, which illustrate a particularmethod by which the robot 120 can avoid obstacles 101 on a panel 100.When the robot 120 reaches the obstacle, one foot (its “near” foot) iscloser to the obstacle 101 than the other foot (its “far” foot). Therobot 120 steps over the obstacle 101 by decoupling the far foot, andflipping the body 130 so the far foot is lifted above the obstacle andcrosses over the obstacle 101.

For example, when the robot 120 encounters the obstacle 101 (FIG. 3 a),the far foot is magnetically decoupled by sliding away (misaligning) itsflux conductor (FIG. 3 b), the body 130 is flipped so that the robot 120straddles the obstacle 101 (FIGS. 3 c to 3 e), and the decoupled foot islowered (FIGS. 3 f and 3 g). All along, the driver 160 remains clampedto the robot 120 by the magnetic coupling between the near foot and itsflux conductor.

The decoupled flux conductor is then slid along the chassis 170 of thedriver 160 until it displaces the other flux conductor (FIGS. 3 h and 3i). The flux conductors may be mounted to the chassis 170 via prismaticjoints in offset planes that allow the flux conductors to pass eachother without interference. This permits the flux conductors to moveindependently of the chassis 170. In this manner, the driver 160 remainsclamped to the robot 120 even as the one flux conductor is beingdisplaced with the other flux conductor. The displaced flux conductor isthen slid forward until it is magnetically coupled with the forward foot(FIG. 3 j).

The remaining steps (FIGS. 31 to 3 p) mimic the initial flipping of therobot over the obstacle. In this manner, the robot 120 moves from oneside of the obstacle (FIG. 3 a) to the other side of the obstacle (FIG.3 p).

Reference is now made to FIG. 4 a-4 h, which illustrate anotherparticular method by which the robot 120 can avoid obstacles. When therobot 120 encounters an obstacle 101 on the panel 100, the foot nearestthe obstacle is decoupled and lifted above the obstacle 101. The robot120 is then moved so the decoupled foot moves past the obstacle 101.

For example, when the robot 120 encounters the obstacle 101 (FIG. 4 a),the foot nearest the obstacle 101 is lifted away from its flux conductor(thereby decoupling it from its flux conductor) and raised above theobstacle 101 (FIG. 4 b). The robot 120 is pulled forward until theraised foot moves past the obstacle 101 (FIG. 4 c). The raised foot isthen lowered and recoupled with its flux conductor (FIG. 4 d). At thispoint, the robot 120 is straddling the obstacle 101. The remaining steps(FIGS. 4 e to 4 h) mimic the initial stepping over the obstacle 101.Throughout this process, the driver 160 remains magnetically coupled tothe robot 120.

A system herein is not limited to the robot 120 and driver 160 describedabove. In some embodiments, joints having several degrees of freedom maybe used instead of the revolute joints 132 and 134, and more complexlinkages than the feet 140 and 145 may be used. In some embodiments, aflux conducting device may include magnets instead of the fluxconductors 180 and 185. In some embodiments, the driver 160 may bereplaced by a gantry or other system for moving the flux conductingdevice along the exterior surface of the panel 100.

A system herein is not limited to any particular application. However,one application of special interest to the applicants is manufacturingoperations on aircraft structures. One such structure is a wing box.

Reference is now made to FIG. 5, which illustrates a wing bay 510 of awing box (the wing box has a plurality of wing bays 510). The wing bay510 includes top and bottom skin panels 520 and 530 and stringers 540extending across the skin panels 520 and 530. An access port 550 islocated in the bottom skin panel 530. The access port 550 leads to aconfined interior space. Fasteners 560 attach ribs 570 and 580 to thetop and bottom skin panels 520 and 530.

Reference is now made to FIG. 6, which illustrates a system 610including inner and outer robots 620 and 630 for performing fasteningoperations on a wing box (only the bottom skin panel 530 and a stringer540 of the wing box are shown). The inner robot 620 carries an inner endeffector 625 for performing fastener termination (e.g., sleeve and nutinstallation). The outer robot 630 carries an outer end effector 635 forperforming drilling and fastener insertion at target locations on thewing box.

The inner robot 620 incorporates the robot 120 described above. Theinner robot 620 may perform either the flipping function or the steppingfunction. One advantage of stepping over a stringer 540 in the mannershown in FIGS. 4 a-4 h (as opposed to flipping in the manner shown inFIGS. 3 a-3 p) is that the inner end effector 625 is always pointingdownward. Moreover, stepping across the stringer 540 allows the innerrobot 620 to operate within the limited height of the wing box. However,the flipping makes it easier to load the inner robot 620 into the wingbox, as will be described below. The following description of FIG. 6 ismade in connection with a stepping operation.

The outer robot 630 includes the drive 160 described above. Since theinner robot 620 only performs a stepping operation, the flux conductorsneed not be configured to slide along the chassis.

A clamping force is achieved by the magnets of the inner robot 620 andthe flux conductors of the outer robot 630. An additional clamping forcemay be provided by configuring the end effectors 625 and 635 to bemagnetically attracted (e.g., a steel plate on the inner end effector625 and an electromagnet on the outer end effector 635).

A lifting platform 640 lifts the inner and outer robots 620 and 630 suchthat the inner robot 620 is inside the wing box and the outer robot 630is outside of the wing box. Once lifted, the inner robot 620 is in aposition to move over the interior surface of the panel 530, and theouter robot 630 is in a position to move over the exterior surface ofthe panel 530. For instance, the lifting platform 640 may include aC-shaped structure 645 having an upper member 647. The inner and outerrobots 620 and 630 are clamped to the upper member 647, and the clampedrobots 620 and 630 are lifted until the upper member 647 is co-planarwith the skin panel 530.

Once lifted, the outer robot 630 moves onto the outer surface of theskin panel 530, while it pulls the inner robot 620 onto the interiorsurface of the skin panel 530 (A and B). The inner robot 620 holds theouter robot 630 against gravity. The robots 620 and 630 move along thepanel 530 until the inner robot 620 encounters a stringer 540. The innerrobot 620 steps over the stringer 540 while holding the outer robot 630against gravity (C and D). After moving to all target locations andperforming all fastening operations within the wing box, the inner andouter robots 620 and 630 return to the access port 550 and exit the wingbox (E).

The inner robot 620 is pulled via flux by the outer robot 630 in anydirection that the outer robot 630 moves. Thus, the inner robot 620 maybe pulled in the direction of the arrows in FIG. 6 (e.g., across thestringer 540), and it may be pulled in a direction orthogonal to thearrows (e.g., pulled along the length of the stringer 540).

The inner and outer robots 620 and 630 may be controlled by an externalcontroller 650. The controller 650 may communicate wirelessly with theinner robot 620. The inner and outer robots 620 and 630 may becontrolled to perform the functions illustrated in FIG. 7.

Reference is now made to FIG. 7, which illustrates a method ofmanufacturing a wing box. At block 710, the wing box is pre-assembled.During pre-assembly, faying (i.e., overlapping) surfaces of wing boxparts (e.g., spars, skin panels, and ribs) may be covered with sealantand pressed together. The sealant eliminates gaps between the fayingsurfaces to facilitate burr less drilling. The pressed-together parts ofthe wing box may then be fastened (temporarily or permanently) withinstrumented fasteners disclosed in assignee's U.S. Pat. No. 7,937,817issued May 10, 2011. In one embodiment, an instrumented fastenerincludes one or more light sources (e.g., light-emitting diodes)configured to produce light beacons in opposite directions. Informationregarding the instrumented fastener (e.g., fastener number) may beencoded in the light beacons.

At block 720, the inner and outer robots 620 and 630 are paired andpositioned on the lifting platform 640. At block 730, the platform 640lifts the inner robot 620 through the access port 550 and into a wingbay of the wing box.

At block 740, the inner and outer robots 620 and 630 are automaticallyunloaded and moved until their inner and outer end effectors 625 and 635are positioned over a target fastener location. The inner and outerrobots 620 and 630 may use vision systems and the instrumented fastenersto position and orient the end effectors 625 and 635 as described inassignee's U.S. Ser. No. 12/117,153 filed May 8, 2008 (now U.S. Pat. No.8,301,302), the specification of which is incorporated herein byreference. The light beacons are directed inside and outside the wingbay, so they can be sensed by the inner and outer robots 620 and 630.

At block 750, precise positioning of the end effectors 625 and 635 withrespect to the target location is performed. In some embodiments, theouter robot's traction system alone can achieve the precise positioning.In other embodiments, additional means (e.g., Lorentz force actuators)may be used in addition to the traction system to achieve the precisepositioning.

At block 760, with the inner and outer robots 620 and 630 clampedtogether and against the skin panel 530, the outer end effector 635performs burr-less drilling at the target location. Countersinking mayalso be performed. The outer end effector 635 then inserts a fastenerthrough the drilled hole.

At block 770, the inner end effector 625 terminates the end of theinserted fastener. For example, the inner end effector 625 installs asleeve and nut onto the fastener.

If additional fastening operations are to be performed (block 780), theend effectors 625 and 635 are moved to a new target location and theoperations at blocks 740-770 are repeated. The outer robot 630 may beturned to orient the inner robot 620 and it may be pulled to move theinner robot 620 towards a new target location.

After the last fastening operation in the wing bay has been performed(block 780), the inner and outer robots 620 and 630 are returned to theaccess port 550, and automatically loaded onto the lifting platform 640(block 790). The inner robot 620 is lowered out of the wing bay (block790), and the inner and outer robots 620 and 630 are moved to the accessport of another wing bay (blocks 785 and 730). The operations at blocks740-780 are repeated until fastening operations have been performed oneach wing bay of the wing box (block 785).

A system and method herein may use an inner robot 620 that performs aflipping operation instead of a stepping operation. Using a flippingoperation, the inner robot 620 can be automatically loaded into a wingbay as illustrated in FIGS. 8 a-8 d.

As shown in FIG. 8 a, the inner and outer robots 620 and 630 are liftedup to the wing box by a lift platform 810 having a magnet bank 812 thatis engaged with one bank of the inner robot's magnets. This allows theinner robot 620 to flip once it has been placed through the access port.

As shown in FIGS. 8 b and 8 c, the inner robot 620 flips to engage itsmagnets with the flux conductors of the outer robot 630. The magnet bank812 of the lift platform 810 is then disengaged from the inner robot 620

(FIG. 8 c). As shown in FIG. 8 d, after the inner robot 620 completes aflip, the lift platform 810 is lowered. The inner robot 620 can beautomatically unloaded from the wing bay by reversing the procedureillustrated in FIGS. 8 a-8 d.

Reference is made to FIG. 9, which illustrates an embodiment of an innerrobot 910 for performing fastener termination operations (the outerrobot is outlined in phantom). The inner robot 910 includes a bridge 920supported at opposite ends by first and second posts 930 and 935. Theposts 930 and 935 are pivoted to the bridge 920. Each post 930 and 935terminates in a magnet base 940 and 945.

Each magnet base 940 and 945 may include a Halbach array of rare earthpermanent magnets. The Halbach array is a specific permanent magnetconfiguration that achieves maximum flux.

The inner robot 910 is shown fastening a rib web 580 to a skin panel530. The bridge 920 carries a multi-function end effector 950 includinga vision system and nut/sleeve installation tool. The end effector 950is movable along Y and Z rails 960 and 970 in Y and Z directions forsleeve and nut installation tasks. The installation tool is moved over afastener end 902, and a sleeve and nut 904 are placed over the fastener902.

The inner robot 910 and the outer robot may also include Lorentz forceactuators (not shown) for fine positioning. Two sets of coils andpermanent magnets may be located on the inner robot 910 and the outerrobot and are directed in such a way that driving forces are generatedin both X and Y directions. The coils are preferably mounted on theouter robot and the permanent magnets are preferably installed on theinner robot 910 so the inner robot 910 remains passive. Running acurrent through a coil generates an equal and opposite Lorentz forcebetween the inner robot 910 and the outer robot. The Lorentz force iscontrolled to precisely position the robots.

The inner robot 910 further includes an on-board controller (not shown)for controlling the inner robot 910 to operate the end effector, senseobstacles, determine when its end effector 950 is precisely positionedover a target, and communicate with an external controller. The externalcontroller commands the movement of the outer robot, controls thecurrent through the Lorentz actuators, etc.

A system herein replaces manual assembly tasks for wing boxes and otherconfined spaces. It can perform thousands of fastening operations muchfaster than manual labor. The system operates within the spaceconstraints of a wing box. It satisfies extremely tight aircrafttolerances.

The robotic operation not only increases productivity, but it alsoreduces worker hardship. Manually installing nuts/sleeves inside theconfined space of a wing box is ergonomically challenging.

A system herein is not limited to fastening operations that involvebolts and nuts. Other fastening operations involve, without limitation,riveting.

A system herein is not limited to fastening operations. A system hereinmay be used to perform other manufacturing operations such as sealantapplication, cleaning, painting and inspection.

A system herein is not limited to an aircraft. A system herein may beapplied to containers, autos, trucks, ships, and other structures havingconfined spaces. For instance, inner and outer robots may be used toinspect the insides of cylinders that hold fluids.

1. A system comprising: a driver robot having a body with a pair ofspaced apart flux conductors; and a follower robot having an articulatedbody with a pair of spaced apart magnets, the magnets coupled to theflux conductors when the articulated body is in an engaged position, oneof the magnets decoupled from one of the flux conductors when thearticulated body is in a flipping or stepping position.
 2. The system ofclaim 1, further comprising a controller for controlling the followerrobot to flip after the one magnet has been decoupled.
 3. The system ofclaim 1, further comprising a controller for controlling the followerrobot to step after the one magnet has been decoupled.
 4. The system ofclaim 1, further comprising a first controller for the driver robot anda second controller for the follower robot, the first controller causingthe driver robot to move along a surface and pull the follower robotalong the surface, the second controller causing the follower robot tosense obstacles on the surface, the first and second controllerscommunicating to enable the follower robot to decouple the one magnetfrom the driver robot, lift the decoupled magnet away from the panel andabove a sensed obstacle, and move past the sensed obstacle.
 5. Thesystem of claim 4, wherein the second controller further causes thefollower robot to lower the decoupled magnet back onto the surface afterthe obstacle has been avoided; and magnetically recouple the decoupledmagnet to one of the flux conductors of the driver robot.
 6. The systemof claim 4, wherein the controllers communicate to cause the robots todecouple a far one of the magnets from the sensed obstacle, and thefollower robot to flip so that the decoupled magnet moves past thesensed obstacle.
 7. The system of claim 6, wherein the first and secondflux conductors are slidable along the body in separate planes; andwherein the first controller causes the decoupled magnet to be recoupledby sliding the flux conductor further from the obstacle to displace theflux conductor closer to the obstacle, and then sliding the displacedconductor to recouple with the decoupled magnet.
 8. The system of claim4, wherein the controllers communicate to cause a near one of themagnets to the sensed obstacle to be decoupled and lifted above thesensed obstacle, and the driver robot to pull the follower robot so thedecoupled magnet moves past the sensed obstacle.
 9. The system of claim1, wherein the flux conductors are mounted to a chassis via prismaticjoints in offset planes that allow the flux conductors to pass eachother without interference.
 10. The system of claim 1, wherein themagnets apply force sufficient to hold the driver robot against gravity.11. The system of claim 1, wherein the driver robot further has atraction drive for moving the flux conductors along a surface.
 12. Thesystem of claim 1, wherein both robots include Lorentz force actuatorsfor fine positioning.
 13. The system of claim 1, further comprising anend effector carried by the driver robot and configured to performdrilling and fastener insertion; and an end effector carried by thefollower robot and configured to perform fastener termination.
 14. Thesystem of claim 13, further comprising a plurality of instrumentedfasteners, the robots configured to use the instrumented fasteners forpositioning the end effectors.
 15. The system of claim 1, furthercomprising a lifting platform for lifting the robots while the robotsare paired.
 16. A method of using the system of claim 15, comprisingautomatically unloading the follower robot onto a structure, includingusing the lifting platform to raise the robot to the structure, andcommanding the follower robot to perform a flip or step off the platformand onto the structure.
 17. The method of claim 16, wherein the followerrobot does a flip or step onto an inner surface of the structure, andwherein the driver robot moves along an outer surface of the structurewhile magnetically coupled to the follower robot.
 18. The method ofclaim 17, wherein both the flip and the step include magneticallydecoupling a first magnet of the follower robot, moving the driver robotonto the outer surface, and moving the decoupled magnet onto the innersurface so it magnetically recoupled with the driver robot.